@kitware/vtk.js/Rendering/OpenGL/RenderWindow/ContextProxy.js

Visualization Toolkit for the Web

// This is used to access the underlying 3D context
var GET_UNDERLYING_CONTEXT = '__getUnderlyingContext';
function createContextProxyHandler() {
  var cache = new Map();
  var getParameterHandler = {
    apply: function apply(target, gl, args) {
      if (cache.has(args[0])) {
        return cache.get(args[0]);
      }

      return target.apply(gl, args);
    }
  }; // only supports single-value setters

  function cachedSetterHandler(key) {
    return {
      apply: function apply(target, gl, args) {
        cache.set(key, args[0]);
        return target.apply(gl, args);
      }
    };
  } // When a property is accessed on the webgl context proxy,
  // it's accessed is intercepted. If the property name matches
  // any of the keys of `propHandlers`, then that handler is called
  // with the following arguments: (gl, prop, receiver, propValue)
  // - gl (WebGL2RenderingContext): the underlying webgl context
  // - propName (string): the property name
  // - receiver (Proxy): the webgl context proxy
  // - propValue (unknown): the value of `gl[propName]`


  var propHandlers = Object.create(null); // Sets getParameter(property) as a cached getter proxy.
  // propValue.bind(gl) is to avoid Illegal Invocation errors.

  propHandlers.getParameter = function (gl, prop, receiver, propValue) {
    return new Proxy(propValue.bind(gl), getParameterHandler);
  }; // Sets depthMask(flag) as a cached setter proxy.


  propHandlers.depthMask = function (gl, prop, receiver, propValue) {
    return new Proxy(propValue.bind(gl), cachedSetterHandler(gl.DEPTH_WRITEMASK));
  };

  return {
    get: function get(gl, prop, receiver) {
      if (prop === GET_UNDERLYING_CONTEXT) return function () {
        return gl;
      };
      var value = Reflect.get(gl, prop, gl);

      if (value instanceof Function) {
        // prevents Illegal Invocation errors
        value = value.bind(gl);
      }

      var propHandler = propHandlers[prop];

      if (propHandler) {
        return propHandler(gl, prop, receiver, value);
      }

      return value;
    }
  };
}
var ContextProxy = {
  createContextProxyHandler: createContextProxyHandler
};

export { GET_UNDERLYING_CONTEXT, createContextProxyHandler, ContextProxy as default };